Multi-execution resource graphics processor

ABSTRACT

A dynamically scheduled parallel graphics processor comprises a spreader that creates graphic objects for processing and assigns and distributes the created objects for processing to one or more execution blocks. Each execution block is coupled to the spreader and receives an assignment for processing a graphics. object. The execution block pushes the object through each processing stage by scheduling the processing of the graphics object and executing instruction operations on the graphics object. The dynamically scheduled parallel graphics processor includes one or more fixed function units coupled to the spreader that are configured to execute one or more predetermined operations on a graphics object. An input/output unit is coupled to the spreader, the one or more fixed function units, and the plurality of execution blocks and is configured to provide access to memory external to the dynamically scheduled parallel graphics processor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to the following copending U.S utilitypatent applications: (1) U.S. Patent Application entitled “SYSTEM ANDMETHOD TO MANAGE DATA PROCESSING STAGES OF A LOGICAL GRAPHICS PIPELINE,”filed on Aug. 8, 2005, under Express Mail Labe EV559572568US; (2) U.S.Patent Application entitled “METHOD FOR PROCESSING VERTEX, TRIANGLE, ANDPIXEL GRAPHICS DATA PACKETS,” filed on Aug. 8, 2005, under Express MailLabel EV559572660US; and (3) U.S. Patent Application entitled “GLOBALSPREADER AND METHOD FOR A PARALLEL GRAPHICS PROCESSOR,” filed on Aug. 8,2005, under Express Mail Label EV559572673US. Each of these patentapplications is entirely incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to an architecture for computerprocessors and computer networks and, in particular, to a system, andmethod for the creating and dynamic scheduling of multiple stream dataprocessing tasks for execution in a parallel processor.

BACKGROUND

Microprocessor designers and manufacturers continue to focus onimproving microprocessor performance to execute increasingly complexsoftware, which delivers increased utility. While manufacturing processimprovements can help to increase the speed of a microprocessor byreducing silicon geometrics, the design of the processor, particularlythe instruction execution core, relates to processor performance.

Many microprocessors use instruction pipelining to increase. instructionthroughput. An instruction pipeline processes several instructionsthrough different phases of instruction execution concurrently, using anassembly line approach. Individual function blocks such as a decodeblock, as a nonlimiting example, may be further pipelined into severalstages of hardware, with each stage performing a step in the instructiondecode process on a separate instruction. Thus, processor hardwarepipelines can be deep with many distinct pipeline stages.

Another method to improve instruction execution speed is known as“out-of-order” execution. Out-of-order execution provides for theexecution of instructions in an order different from the order in whichthe instructions are issued by the compiler in an effort to reduce theoverall execution latency of the program including the instructions. Oneapproach to out-of-order instruction execution uses a technique referredto as “register scoreboarding,” in which instructions are issuedin-order, but executed out-of-order. Another form of out-of-orderscheduling employs a technique known as “dynamic scheduling.” For aprocessor that provides dynamic scheduling, even the issue ofinstructions to execution hardware is rescheduled to be different fromthe original program order. The results of instruction execution may beavailable out of order, but the instructions are retired in programorder. Yet, instruction pipelining in out-of-order techniques, such asdynamic scheduling, may be used separately or together in the samemicroprocessor.

Dynamic scheduling of parallel instruction execution may include specialassociative tables for bookkeeping instruction and functional unitstatus as well as the availability of a result of a particularinstruction for usage as an input operand according to prescribedinstructions. Scheduling hardware uses these tables to issue, execute,and complete individual instructions.

The scope of the dynamic scheduling of parallel instruction execution isinstruction level parallelism (ILP), which has been extended to multiplethreads (hyperthreading or simultaneous multithreading (SMT)). Thistechnique provides hardware assisted dispatch and execution of multiplethreads providing multiple instructions per clock issue to process in aparallel functional unit. Dynamic scheduling hardware providessimultaneous instruction issue from the multiple active threads.

Scheduling hardware may use scoreboards for the bookkeeping of threadand instruction status to trace dependencies and to define the moment ofissue and execution. In addition, threads may be suspended because oflong latency cache misses or other I/O reasons. Nevertheless, as anonlimiting example, the scoreboard may be comprised of an instructionstatus, a functional unit status, as well as a register result status.All three of these tables interact in the process of instructionexecution by updating their fields each clock cycle. In order to passthe stage and change status of an instruction, certain conditions shouldbe fulfilled and certain actions should be taken on each stage.

Register renaming is another technique that may be implemented toovercome name dependency problems when architecture registers namespaceis predetermined, which enables instructions to be executed in parallel.According to a register renaming technique, a new register may beallocated each time an assignment is made to a register. When aninstruction is decoded, the hardware checks the destination field andrenames the architecture register name space. As a nonlimiting example,if register R3 is assigned a value, a new register clone R3′ may beallocated and all reads of register R3 in the following instructions aredirected to clone R3′ (replacing architecture name by clone name).

In continuing this nonlimiting example, when a new assignment is made toregister R3, another register clone R3″ is allocated and the followingreferences are redirected to new clone R3″. This process continues withall input instructions. This process not only removes name dependencies,but it also makes the processor appear to have more registers and mayincrease the instruction level parallelism so that more parallel unitsmay operate.

Register renaming may also be used by reorder buffers so as to extendthe architecture register space and create multiple copies of the sameregister associate with different commands. This results in the abilityto provide out-of-order with in-order completion.

When an instruction is decoded, it may be assigned a reorder bufferentry associated with the appropriate function unit. The destinationregister of the decoded instruction may be associated with the allocatedreorder buffer entry, which results in renaming the register. Theprocessor hardware may generate a tag to uniquely identify this result.The tag may be stored in the reorder buffer entry. When a subsequentinstruction refers to the rename destination register, it may receivethe value or the tag stored in the reorder buffer entry, depending uponwhether or not the data is received.

A reorder buffer may be configured as a content addressable memory (CAM)where the tag is used for a data search. In application, a destinationregister number of a subsequent instruction may be applied to a reorderbuffer and the entry containing this register number may also beidentified. Once identified, the calculated value is returned. If thevalue has not been computed, the tag, as described above, may bereturned instead. If multiple entries contain this register number, thenthe latest entry is identified. If no entries contain the requiredregister number, then the architecture register file is used. When theresult is produced, the result and tag may be broadcasted to allfunctional units.

Another processing approach involves real-time scheduling andmultiprocessor systems. This configuration involves loosely coupled MIMDmicroprocessors, where each processor has its own memory and I/Ochannels. Several tasks and subtasks (threads) may run on these systemssimultaneously. However, the tasks may include synchronization in sometype of ordering to keep the intended processing pattern. Plus, thesynchronization needed may be different for various processing patterns.

Unlike instruction level parallelism processors, real-time schedulingprocessors use processor assignment to task in threads (resourceallocation). With the instruction level parallelism configuration, theremay be specialized functional blocks with few of them duplicated, whichmeans that instruction assignment for distribution is relatively simpledepending upon the number of available slots and the type ofinstruction.

However, for multiprocessor systems of the MIMD type, all processors aretypically similar and have a more complicated task assignment policy. Atleast one nonlimiting approach is to consider the MIMD structure as aprocessor pool, which means to treat the processor as a pooled resourceand assign processes to processors depending upon availability of memoryand computational resources.

There are at least two methodologies for distributing tasks and threadsin this environment. The first is static assignment, which occurs wheneach type of task or thread is preassigned to a particular processor orgroup of processors. The second configuration is dynamic assignment, assimilarly described above, which calls for tasks being assigned to anyprocessor from the pool depending upon available resources and taskpriority. In this configuration, the multiprocessor pool may havespecial dispatch cues where tasks and threads are waiting for assignmentand execution, as well as for I/O event completion. Also in thisconfiguration, threads are parts of a task, and some of the tasks may besplit into the several threads that may be executed in parallel withsome synchronization on data and order. Thus, the threads in general mayexecute separately from the rest of the process. Also, an applicationcan be a set of threads that cooperate and execute concurrently in thesame address space but using different processors. As a result, threadsrunning concurrently on separate processors may yield dynamic gain inperformance.

In a multiprocessor configuration, thread scheduling may be accomplishedaccording to load sharing techniques. Load sharing may call for the loadbeing distributed evenly across the various microprocessors in the pool.As a result, this ensures that no microprocessor is idle.

Multiprocessor thread scheduling may also use some of the staticscheduling techniques described above, such as when a thread is assignedto a specific processor. However, in assigning certain threads to aspecific processor, other processors may be idle while the assignedprocessor is busy, thereby causing the assigned thread to sit idlywaiting for its assigned processor to become free. Thus, there may beinstances where static scheduling results in inefficiency in theprocessor.

Dynamic scheduling of processors may be implemented in an objectoriented graphics pipeline. An object is a structured data itemrepresenting something travelling down a logical pipeline, such as avertex of a triangle, patch, pixel, or video data. At the logical level,both numeric and control data may be part of the object, though thephysical implementation may handle the two separately.

In a graphics model, there are several types of objects that may beprocessed in the data flow. The first is a state object, which containshardware controlled information and shader code. Second, a vertex objectmay be processed, which contains several sets of vertices associatedwith numerical control data. Third, a primitive object may be processedin the data flow model which may contain a number of sets of primitive'associated numerical and control data. More specifically, a primitiveobject may include a patch object, triangle object, line object and/orpoint object. Fourth, a fragment object may be part of the data flowmodel which may contain several sets of pixel associated numerical andcontrol data. Finally, other types of objects such as video data may beprocessed in a data flow model as well.

Each type of object may have a set of possible operations that may beperformed on it and a (logically) fixed data layout. Objects may existin different sizes and statuses, which also may be known as levels orstages to represent the position they have reached in the process inpipeline.

As a nonlimiting example, the levels of an object may be illustrated ona triangle object, which initially has three vertices that point to theactual location of vertex geometry and attribute data. When thereferences are resolved (check caches and retrieve data from API buffersif needed), the object level is upgraded so that the object is sentthrough other stages. The level of upgrade normally may reflect theavailability of certain data in the object structure for immediateprocessing. An upgraded level includes the previous level in most cases.

One of ordinary skill in the art would know that there may generally betwo types of sizes (layouts) of an object. A first is a logical layout,which may include all data structures. The logical layout may remainunchanged from the moment of object creation through termination. Asecond type of layout for objects is a physical layout that shows thedata structure is available for immediate processing, which operates tomatch the logical layout in the uppermost level.

Both the logical and physical layouts may be expressed in terms offrames and buffers—logical frames and physical buffers. Logical framesmay be mapped to physical buffers to make data structures available forimmediate processing. Each object initially may contain few logicalframes and one of them may be mapped to a physical buffer. All otherframes used in later stages may not be mapped so as to save memoryresources on the chip. Yet both frames and buffers may have variablesize with flexible mapping to each other.

An object may refer to data held within other objects in the system.Pipeline lazy evaluation schemes track these dependencies and use themto compute the value stored inside an object on demand. Objects of thesame type may be processed in parallel independent cues. Alternatively,a composite object may be created containing several vertices,fragments, or primitives to process in SIMD mode.

For graphics processing applications, the features described above havehistorically included fixed function and programmable hardware basedpipeline solutions. However, these linear solutions oftentimes lead toinefficiencies resulting from the static configuration of the graphicspipeline. When the bandwidth of a particular stage as described abovedoes not change during the execution time of the frame generation,inefficiencies and idle time in the processor are introduced, therebydecreasing the overall efficiency. This inefficiency is compounded in anapplication involving multiple parallel processors.

Thus, there is a heretofore-unaddressed need to overcome the problem ofdynamic creating and execution management of multiple logic graphicpipelines in an MIMD structure of parallel multithread processors. Thereis a further need for improved resource utilization in parallelprocessing to achieve higher performance, which may be previouslyattributed to poor allocation and scheduling protocol resolution.

SUMMARY

This disclosure relates to a dynamic scheduling unit and method for aparallel graphics processor, which may process vertex entities, triangleentities, and pixel entities, as nonlimiting examples. The disclosureprovides for the dynamic scheduling of multiple stream data processingtasks related to vertexes, triangles, and pixels. Stated another way, aparallel processor processes these entities in parallel simultaneously.

A dynamic scheduling unit for a parallel graphics processor comprises aspreader that creates graphic objects for processing. The spreaderassigns and distributes the created objects for processing to one ormore execution blocks. Each execution block receives an assignment forprocessing a graphics object and pushes the object through eachprocessing stage by scheduling the processing of the graphics object andexecuting instruction operations on the graphics object.

The dynamic scheduling unit includes one or more fixed function unitscoupled to the spreader that are configured to execute one or morepredetermined operations on a graphics object. An input/output unit iscoupled to the spreader, the one or more fixed function units, and theplurality of execution blocks and is configured to provide access tomemory external to the dynamic scheduling unit. This dynamic schedulingunit allocates resources for increased efficient processing, therebyresulting in improved performance.

Other systems, methods, features, and advantages of this disclosure willbe or become apparent to one with skill in the art upon examination ofthe following drawings and detailed description. It is intended that allsuch additional systems, methods, features, and advantages be includedwithin this description, be within the scope of this disclosure, and beprotected by the accompanying claims.

DESCRIPTION OF THE DRAWINGS

Many aspects of the disclosure can be better understood with referenceto the following drawings. The components in the drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the present disclosure.

FIG. 1 is a diagram of an abstract hardware model of the object-orientedarchitecture of the current disclosure.

FIG. 2 is a diagram of the three levels of dynamic scheduling in theobject oriented architecture model of FIG. 1.

FIG. 3 is a diagram of the object oriented architecture model of FIG. 1shown with additional operational blocks associated with the blocks ofFIG. 1.

FIG. 4 is a diagram of the queue and cache controller of FIG. 3.

FIG. 5 is an execution flow diagram of the object-oriented architectureinteraction in a vertex processing sequence, as executed by theobject-oriented architecture of FIG. 1.

FIGS. 6 and 7 illustrate the object-oriented architecture interactionfor a triangle processing sequence for the model of FIG. 1.

FIGS. 8 and 9 depict the object-oriented architecture model interactionin a. pixel processing sequence for the model of FIG. 1.

FIG. 10 is a diagram of a nonlimiting example flowchart depictingallocation of a triangle entity between the global spreader and anexecution block of FIG. 1.

DETAILED DESCRIPTION

As opposed to static scheduling, as described above, dynamic schedulingmay be employed during execution of threads such that a number ofthreads in a process may be altered dynamically by the application.Dynamic scheduling also results in assignment of idle processors toexecute certain threads. This approach improves the use of the availableprocessors and therefore the efficiency of the system.

FIG. 1 is a diagram of an abstract hardware of the object-orientedarchitecture model 10 of the current disclosure. The object orientedarchitecture model 10 of FIG. 1 includes a general-purpose processingportion with a pool of execution blocks that provide local scheduling,data exchange, and processing of entities or objects.

The object-oriented architecture model 10 of FIG. 1 enables the dynamicscheduling for parallel graphics processing based upon the concept ofdynamic scheduling instruction execution, which may be used insuperscalar machines. This concept may be extended to threads andmicrothreads that are fragments of code to be executed on graphics dataobjects. As described herein, the dynamic scheduling approach is mappedto the logical graphics pipeline, where each part processes a specifictype of graphics data object and executes threads containing severalmicrothreads. More specifically, the course grained staging of thegraphics pipeline may match threads on a level of object types, such asvertex, geometry, and pixel, wherein the fine grain staging is comparedto microthreads.

The object-oriented architecture model 10 includes a global schedulerand task distributor 12, which hereinafter is referred to as a globalspreader 12. Global spreader 12 has attached vertex and index streambuffers, a vertex table, and a primitive table, as described in moredetail below (FIG. 3). Global spreader 12 is coupled to the variouscomponents of the object oriented architecture model 10 via a datatransport communication system 13, as one of ordinary skill in the artwould know. The data transport communication system 13 couples allcomponents of the architecture, as shown and described in FIG. 1.

Execution blocks 15, 17, and 19 provide local scheduling, data exchange,and processing of entities, as distributed by global spreader 12. Thelogical construction and operation of execution blocks 15, 17, and 19are discussed in more detail below.

Fixed function hardware and cache unit 21 (hereinafter “fixed functionunit 21”) includes dedicated graphics resources for implementing thefixed function stages of graphics processing, such as rasterization,texturing, and output pixel processing parts. Additionally, an I/Ocommon services and bulk cache block 23 is included in theobject-oriented architecture model 10 of FIG. 1, which may be configuredto comprise a command stream processor, memory and bus access, bulkcashes, and a display unit, all as nonlimiting examples.

Although discussed in more detail below, the global spreader 12 mayutilize the data transport 13 for communicating with one or more ofexecution blocks 15, 17, and 19. However, the execution blocks 15, 17,and 19 may also communicate with each other via data transport 13according to the various tasks and processes for which the executionblocks are assigned to execute by global spreader 12.

Global spreader 12 interacts with all of the execution blocks in theobject-oriented architecture model 10 and traces available resources inthe execution blocks 15, 17, and 19 with clock resolution. The taskdistribution configuration of the global spreader 12 may be fullyprogrammable and adapted on a per frame monitoring basis of eachexecution block's profile.

FIG. 2 is a diagram of the three levels of dynamic schedulingimplemented in the object oriented architecture model 10 of FIG. 1. Atthe global scheduling level, global spreader 12 operates with varioustables and is also involved in new entity creation and logical frameassignment, as well as in the distribution to the various executionblocks 15, 17, and 19 and physical memory allocation (on the globalscheduling level). Thus, as discussed above, the global spreader 12interacts with the various execution blocks 15, 17, and 19 of FIG. 1,which are involved in the local scheduling level, as shown in FIG. 2. Atthe local scheduling level, a local task scheduler includes a localscoreboard. The local scoreboard comprises a queue and cache controllerwith a stage parser that operates to push entities from stage to stagethrough the processing pipeline (see FIGS. 5-9) as well as physicalmemory allocation for upgraded status entities throughout the executionof various processes.

At the instruction execution scheduling level, the execution blockscontain a numeric streampipe thread controller 32, which controlsnumerical processing of threads defined by stage parser 82. Theinstruction execution level also includes a data move controller 34,which enables execution of multiple threads across multiple executionblocks and implements multichannel I/O control. Stated another way, thedata move controller 34 sends and receives data to/from other executionblocks as well as the global spreader 12.

All levels, including the global scheduling level, local schedulinglevel, and instruction execution level, include hardware controllers toprovide dynamic scheduling with clock resolution. Moreover, the globaland local scheduling controllers cooperate in computational resourceallocation.

FIG. 3 is a diagram of the object-oriented architecture model 10 of FIG.1 depicted with additional operational blocks associated with the globalspreader 12, execution block 15, fixed function block 21, and common I/Oservices and bulk caches block 23. As shown in FIG. 3, the globalspreader 12 includes a primitive table 41 (a table that containsreferences to basic elements), a vertex descriptor table (vertexallocation in all execution blocks) 43, and an input vertex buffer andindex buffer 46. As discussed above, the global spreader 12 is the mainupper level scheduling unit that distributes workload to all executionblocks 15, 17, 19, etc. by using the status information of the executionblocks and data received from the fixed function units 21. Ininteraction with the execution block' local queue-cache controller 51,as shown in FIG. 4, the global spreader 12 creates new entities to pushinto a logical pipeline.

The global spreader 12 controls data distribution between all executionblocks and uses the principle of locality of “producer-consumer” datareferences. As a nonlimiting example, global spreader 12 attempts toallocate vertex entities with associated triangle entities anddistribute pixel packets from a particular triangle to an executionblock that has triangle entity data. If this particular execution blockdoes not have enough resources for allocation, vertex or triangle datamay be copied to another execution block where triangle or pixelentities may have been sent.

In at least one nonlimiting example, the global spreader 12 may receiveat least four types of input requests to arrange processing in theexecution blocks. First, the spreader 12 may receive a packet ofvertices, as generated by the input vertex buffer 46. Second, the globalspreader 12 may receive a packet of triangles, as generated by triangleassembly hardware. The global spreader 12 may furthermore receive apacket of pixels (up to 16 pixels in at least one nonlimiting example),as created by a pixel packer 49, which may be a logical component of thefix function hardware and caches 21. As an additional nonlimitingexample, the global spreader 12 may receive a BEZIER patch (16 verticesin at least one nonlimiting example), as created by the input vertexbuffer 46.

For each type of data that the global spreader 12 receives, the globalspreader 12 maintains and oversees various control information for eachexecution block in the object-oriented architecture model 10. In thisnonlimiting example, as shown in FIG. 3, the object-orientedarchitecture model 10 includes execution blocks 15, 17, 19, 48, and 49.However, one of ordinary skill in the art would know that a greater orlesser number of execution blocks may be included according to thedesired application. Nevertheless, as described above, global spreader12 retains information at least relating to the number of availableexecution blocks at any given moment. Additionally, global spreader 12retains information related to the minimal amount of resources needed tobe free for a new entity of a particular type, as may be set by anexternal driver. The global spreader 12 also establishes the priority ofeach execution block as to receive a particular resource. In at leastone nonlimiting example, the object-oriented architecture hardware model10 may be configured with dedicated execution blocks for certain typesof data and/or entities. Thus, in this instance, the global spreader 12may be aware of these dedications so as to assign particular data tothese execution blocks for processing.

The global spreader 12 also maintains data related to the size of datato be processed and copied to the execution block, as well as priorityinformation related to the data or entity. The global spreader 12 mayalso retain data layout preferences. As a nonlimiting example, whilevertices may implement no data layout preferences, triangles may bebetter constructed with their vertices as well as pixels with thetriangles, therefore constituting a data layout preference. Thus, inthis case, the global spreader 12 retains this information for moreefficient processing.

The global spreader 12 includes a primitive table 41. Each triangle getsits primitive ID, which is stored in the primitive table 41 when thetriangle entity is allocated. In this nonlimiting example, the primitivetable 41 has two fields: PrID (primitive ID) and EB#, which correspondsto the execution block number, where the triangle entity is allocated. Apixel packet communicated from fixed function unit 21 carries a triangleID, which can be used for lookup at the primitive table 41 to determinethe logical location of the original triangle entity.

The global spreader 12 also includes a vertex descriptor table 43, whichis a global vertex bookkeeping table for all execution blocks 15, 17,19, 48, and 49 (in FIG. 3). The vertex descriptor table 43 containsrecords or information about the location of each group of eightvertices (or any number defined by SIMD factor of an execution block),which may be contained in a vertex packet being processed. In at leastone nonlimiting example, the vertex descriptor table may containapproximately 256 records, including such information as the field name,the length of the field, the source of the field, which may, asnonlimiting examples, be the spreader 12, the vertex descriptor tablecontrol, or the queue cache controller 51 in a particular executionblock. The vertex descriptor table 43 also retains destinationinformation for the particular records as well as descriptioninformation about the particular field of data. The vertex descriptortable operates in conjunction with the input vertex buffer and indexbuffer 46 when a vertex packet is received. The global spreader 12creates a vertex entity and initiates transfer between the input vertexbuffer and index buffer 46 and the allocated execution block memory, asdescribed in more detail below.

As a nonlimiting example, if an incoming packet does not fit within theexecution block pool, including execution blocks 15, 17, 19, 48, and 49of FIG. 3, the global spreader 12 may not acknowledge the receiving ofthis data until the global spreader 12 can properly allocate aparticular execution block with enough resources, such as memory space.In this instance, for a given packet of vertices, the global spreader 12may be configured to perform a variety of actions. First, the globalspreader 12 may seek a suitable execution block, such as execution block17, using its resource requirement/allocation information, as describedabove. Alternatively, the global spreader 12 may communicate a requestto a particular execution block, such as execution block 49, to allocatean entity for a received packet of vertices. If the packet of verticesreceived is not indexed, the global spreader 12 may create an index forit in the input vertex buffer 46. Additionally, the global spreader 12may allocate an entry in the vertex table 43 and fill that entry withthe index and number of the entity, as allocated by a particularexecution block. Finally, the global spreader 12 may direct theexecution block data move unit 52 to move the data to a desired locationin the execution block for processing.

Instead of a packet of vertices, if the global spreader 12 receives apacket of triangles that may not fit in a particular execution blockpool, the global spreader 12 may seek to find a suitable execution blockusing the resource requirement/allocation information, as similarlydescribed above for the packet of vertices. Alternatively, the globalspreader 12 may, upon using the indices of the triangle's vertices,retrieve the entity numbers and extract the vertical element numbers.The global spreader 12 may communicate a request to an execution block,such as execution block 19, to allocate an entity for the packet oftriangles. Thereafter, the global spreader 12 may communicate the entitynumbers of the vertices and the element numbers (1-8) to the particularexecution block, such as execution block 19 in this nonlimiting example.

For a given packet of pixels received by global spreader 12, globalspreader 12 may seek to find a suitable execution block using theresource requirement/allocation information, as described above inregard to the packet of triangles and the packet of vertices.Alternatively, the global spreader 12 may communicate a request to aparticular execution block to allocate an entity for the packet ofpixels. In this instance, the global spreader 12 may communicate theentity numbers of the triangles those pixels belong to, as well as theirelement numbers, to the execution block for further processing.

Thus far, focus has been directed to the global spreader 12 and itsfunction. However, focus is now directed to the pool of execution blocksand their manner of communicating with the global spreader 12 andoperating in parallel to each other.

Each execution block contains a queue and cache controller (“QCC”) 51.The QCC 51 provides staging in the data stream processing along withdata linking to numerical and logical processors, such as for floatingpoint and integer calculations. The QCC 51 assists in the management ofa logical graphics pipeline where data entities are created ortransformed at each stage of the processing. As described herein, theQCC 51 comprises an entity descriptor, stage parser, and an addressrename logic table. (Additional QCC components are described anddepicted below.)

For execution block 15, the QCC is shown as reference 51, but isotherwise the same in the remaining execution blocks shown in FIG. 3.QCC 51 has specialized hardware to manage logical FIFOs for dataprocessing stages, as well as for linking the various stages together,as discussed in more detail below. QCC 51 is local to execution block15, and the other QCCs shown in FIG. 3 are local to their respectiveexecution blocks as well. In this manner, each QCC has global referencesto other execution blocks' queues to support global ordering if soconfigured by global spreader 12. Logic in the QCC 51 may cause a datamove unit 52 to move the data between the execution block through itsvarious stages and/or to other components, such as another executionblock 17, 19, 48, or 49, as shown in FIG. 3.

QCC 51 includes a local cache 54. The data in local cache 54 is not, atleast in one nonlimiting example, communicated to any physical FIFO.Instead, all FIFOs are logical with memory references to the variousobjects. As a nonlimiting example, vertex data associated with a vertexpacket may remain in the local cache until the vertex data is processedor will otherwise disappear or be copied to associated triangle entitiesfor further processing, but the vertex data would not remain in localcache 54.

QCC 51 also includes a thread controller 56 that supports multithreadingand can run four or more active threads, therefore providing MIMD aboveSIMD stream type execution at the execution block level. Althoughdescribed in additional detail below, QCC 51 communicates with a streamnumeric pipe and associated registers unit 57 that provide simultaneousexecution of floating point and integer instructions, which processesmultiple data items in the SIMD stream.

As shown in FIG. 3, the fixed function unit 21, in this nonlimitingexample, comprises mostly dedicated fixed function units that have welldefined functionality. In at least one nonlimiting example, the fixedfunction unit 21 includes a pixel packer 49, a tile bypass queue 61, anda reorder buffer 63 with an output tile generator 64 (pixel unpacker).The pixel packer 49 may be configured to reduce the granularity loss onsparse tile processing in the execution block and may also provide pixelpackets with valid pixels. The tile bypass queue 61 may be configured tohold all tile pixels masks, while pixels on those tiles are processed inthe execution block pool. Also, the output tile generator 64 may beconfigured to use the tile pixel mask for unpacking pixel informationreceived in the execution block pool. The reorder buffer 63 restoresinitial order of the pixel packets sent to the execution block pool, asit may also be processed out of order.

FIG. 4 is a diagram of QCC 51 of execution block 15 (or any otherexecution block of FIG. 3) of FIG. 3 with additional components shown.In this nonlimiting example, QCC 51 includes a communication unit 71having both an input portion 73 and an output portion 75 wherein dataand other information may be received from another execution blockand/or output to a different execution block and/or global spreader 12.Communication unit 71 includes a communication controller 77 that maycommunicate data with the data management move machine 52 via bus 79.

Data may also be communicated by bus 79 to the entity descriptor table78, which is configured to contain information about assigned packets'data relation, allocation, readiness, and the current stage ofprocessing. The entity descriptor table 78 includes descriptors ofentities and associated physical buffers for storing data associatedwith each entity and various constants. The entity descriptor table 78,in at least one nonlimiting example, may contain up to 256 records of atleast two types, including a physical buffer entry and an entity entry.All logical FIFOs used for a virtual graphics pipeline are implementedusing the descriptor table 78 and stage parser 82 having a stage pointertable 83.

In at least one nonlimiting example, the entity descriptor table 78 maybe based upon a CAM (content addressable memory) and may use two tothree fields for associative lookup. As a nonlimiting example, thefields may include an entity number field that may be comprised of eightbits and a logical frame number field comprised of four bits. In thisway, the entity descriptor table 78 may be considered as a fullassociative cache memory with additional control state machines updatingsome fields of each record according to conditions in the executionblocks at each clock cycle.

Stage parser 82 includes a stage parser table containing pointers foreach processing stage in a logical pipeline of a graphics processingnonlimiting example, as shown in FIGS. 5-9 and also discussed below.Stage pointers actually point to the entity to be processed next on eachstage. In at least one nonlimiting example, there are two processes thatmay be associated with each stage—a numerical process or an I/O and datamove process. The pointers contained in the stage parser table of stageparser 82 may be used to choose client descriptors with a threadmicroprogram.

When the stage parser table of stage parser 82 generates a dynamicpointer pointing to a particular entity, client descriptor recordcontained in the descriptor table 78 may be loaded to the threadcontroller 56 for numerical stage processing, as described above, whichmay include floating point and integer instructions. Each stage in stagepointer table has a static pointer to a record in the descriptor table,which defines the thread microcode start address and thread parameters.Logical pipeline functionality is configured by those records pointingto different segments of microcode in instruction memory for numericaldata processing.

Alternatively, the stage pointer table of stage parser 82 may contain apointer to I/O and data move process descriptor that may be utilized bythe data management move machine 52 in the case of an I/O process.Although not shown in FIG. 4, the stage parser 82 includes a controllerthat checks at every clock cycle the status of the entities in theentity descriptor table 78 so that the entities may be processed fromstage to stage.

When the QCC 51 operates to communicate data to another execution block,such as execution block 19, the stage parser table may generate apointer value that is associated with a run data move process, which iscommunicated to the I/O and move descriptor register table 85. A rundata transfer request is communicated from the I/O and move descriptorregister table 85 and to the data management microprogram memory 87,which issues an instruction to the data management move machine 52 foraccessing the particular data in the cache memory 88 and sending it tothe designated memory location.

In the case where the stage parser table of stage parser 82 is involvedin a process for the numerical processing of an entity, the stage parsertable of stage parser 82 generates a pointer value for executing anumerical process, which is communicated to the numerical processdescriptor register table 91. The numerical process descriptor registertable 91 communicates with the thread controller 56 for execution of thefloating point or integer sequence of instructions associated with thenumerical process.

The address rename logic table 94 contains address rename informationused to provide flexible mapping of the physical buffers to the cachememory lines 88, as similarly described above. The logic rename tablehas one or more controllers providing activity and updates to the table.The address rename logic table provides virtual type access to localcache memory. More specifically, the logic table 94 converts a physicalbuffer number to a cache address. One of ordinary skill would know thatthe logic table may be configured to operate similarly to a translationlook-aside buffer (TLB) in a virtual memory system.

Data management move machine 52 is responsible for all data load andmoves inside the execution block and interaction with the globalspreader 12, as well as all other execution blocks and fixed functionunit 21, as shown in FIG. 1. In at least one nonlimiting example, athread will not be processed if data is not stored in the executionblock's cache memory 88 and/or loaded to the registers, such as theentity descriptor table 78. As such, the data management move machine 52interacts with the entity descriptor table 78 to acquire the status ofentries in the table so as to provide data requested externally to theexecution block 15, such as for global reference purposes. As anonlimiting example, if one vertex of a triangle is processed in a firstexecution block, for triangle processing purposes, that particularexecution block may seek to copy this vertex information to one or moreother execution blocks where the remaining vertices of the triangle arebeing processed or otherwise reside. In this way, the data managementmove machine 52 provides all interactions of the particular executionblock with global resources, as shown in FIG. 1.

FIG. 5 is an execution flow diagram of the object-oriented architecturemodel 10 of FIG. 1 in a vertex processing sequence. For the vertexobjects, reference is made to an “entity,” which may be equivalent.Logical FIFOs may not necessarily have physical equivalents, as entitiesmay not change a location in the memory once they have been created.Instead, the stage parser 82 uses pointers to descriptor table toidentify an entity so as to push the entity from one state to another.

As shown in the nonlimiting example of FIG. 5, global spreader 12communicates a geometry stream for a vertex processing sequence to thedata management move machine 52 via the input vertex buffer 46 of FIG.3. The global spreader's 12 vertex table 43 communicates an entityallocation request and books the entity in the vertex table 43.Remaining in stage 0, the execution blocks's queue and cache controller51 allocates memory resource for one or more logical frames of theentity in cache memory 88 and establishes an entity descriptor tableitem in table 78. While this entity is allocated, as shown in stage 0,cache lines for the entity are also established in cache memory 88.During this operation, the execution blocks's thread controller andnumerical pipe may be executing other threads, as shown in stage 0.

In stage 1, the vertex geometry batch data load may take place upon thestage parser 82 identifying the vertex entity to be stored in cachememory 88. In this operation, stage parser 82 directs data managementmove machine 52 to obtain the vertex geometry data for cache memory 88.

In stage 2, as shown in FIG. 5, the geometry data loaded in cache memory88 may be accessed according to stage parser 82 so that the threadcontroller 56 and numerical pipe may perform, in this nonlimitingexample, operations according to a transformation shader program. Theresulting data may be stored again in cache memory 88 in stage 2 inadvance of operation in stage 3.

In stage 3, the vertex attributes batch data may be loaded according tothe stage parser 82 directing the data management move machine 52 toplace this data in cache memory 88, as shown in stage 3. At this time instage 3, the execution block's thread controller 56 and numerical pipemay be executing other threads.

In stage 4, the queue and cache controller's stage parser 82 may directthe transformed geometry and raw attributes to be transferred so thatthe attribute transform and lightening shader operation may beperformed. The resulting data may be stored again in cache memory 88, asshown at stage 4 into stage 5.

In stage 5, the transformed data in cache memory 88 may undergo anadditional post-shading operation by the thread controller 56 andnumerical pipe upon receipt of a pointer from stage parser 82 for thevertex entity. Upon exiting the post shader, as shown in stage 5 of FIG.6, the resulting vertex data is again placed in cache memory 88 andsubsequently communicated by the data management move machine 52 toeither another execution block or an assigned memory location as theglobal spreader 12 may direct.

At the conclusion of stage 5, the stage parser 82 initiates a “deleteentity” command to the entity descriptor table so as to delete thevertex entity ID for this operation. Stated another way, the entityreference may be deleted from the vertex queue, but the vertex data mayremain in cache memory 88 so as to be used by triangle entities forother processing operations, as described below. Each of the six stagesdescribed above may take place over several cycles, depending upon themicroinstructions to be executed and the size of the data to be moved.

FIGS. 6 and 7 demonstrate the object-oriented architecture interactionfor a triangle processing sequence for model 10 of FIG. 1. In stage 0,the global spreader 12 may communicate via the data transport bus 13with the data management move machine 52 while also allocating thetriangle entity quest and booking the request in the vertex table 43.The triangle entity creation process may continue in the execution blockQCC 51 by allocating the entity in the entity descriptor table 78 andallocating a memory space in cache memory 88 for the triangle vertexindices and geometry data. During this time, in stage 0, the threadcontroller 56 and numerical pipe may be executing other threads.

In stage 1, the stage parser 82 may point to the triangle entityallocated in stage 0 and also direct the data management move machine 52to receive the triangle geometry data that may be copied to cache memory88 and referenced in the entity descriptor table 78, as shown in stage1. At this same time, however, the thread controller 56 and numericalpipe may still be executing other threads.

In stage 2, the stage parser 82 may direct the loaded triangle geometrydata in cache memory 88 to the numerical pipe with thread controller 56for, in this nonlimiting example, backface culling. The resulting datamay be stored in cache memory 88, as shown in stage 2, with the renamedtriangle entity ID retained in entity descriptor table 78.

In stage 3, the numeric pipe with thread controller 56 may conductprocessing on the vertex data entities, as described above, which mayresult from the stage parser 82 referencing the entity descriptor table78 so that the data move management machine 52 communicates the addressinformation to another execution block that may be processing the vertexentities. In stage 4 (FIG. 7), the triangle vertex attributes that arenow stored in cache memory 88 may be executed via thread controller 56in numerical pipe to perform a triangle clip test/split operation.Again, the resulting data may be stored in cache memory 88 with thequeued entry retained in the entity descriptor table 78.

Continuing in this nonlimiting example, stage 5 operation includes thestage parser 82 referencing the entity descriptor table 78 to a smalltriangle operation in the thread controller 56 and numerical pipe, aswell as a one-pixel triangle setup operation. Cache memory 88 storesdata related to one pixel triangles and triangles that are less than onepixel. As shown in stage 6, the resulting data related to the trianglesis referenced in the entity descriptor table 78 such that a corner iscommunicated by the stage parser 82 to the data management move machine52. Stated another way, the resulting triangle geometry data may beforwarded by bus 13 to the global spreader 12 or to another executionblock for further processing. Just as described above, each stage maytake several clock cycles depending upon the number of microinstructionsto be executed and the data size to be moved.

FIGS. 8 and 9 depict the interaction of the object-oriented architecturemodel 10 in a pixel processing sequence. As shown in FIG. 8, the globalresources of the model 10 of FIG. 1 may establish in the input buffer 46of global spreader 12 an input pixel entity in stage 0. This entitycreation also occurs in the QCC 51 such that a pixel entity ID iscreated in the entity descriptor table 78 and pixel memory is allocatedin cache memory 88, as shown in stage 0. At this time, the threadcontroller 56 and numerical pipe may be executing other threads.

In stage 1, however, stage parser 82, via its stage parser table,fetches the pixel entity ID in the entity descriptor table such that thepixel data in cache memory 88 is communicated to thread controller 56and the numerical pipe for, in this nonlimiting example, a pixelinterpolation setup operation. The resulting data is returned to cachememory 88 as the pixel interpolation parameters. Also, stage parser 82cues the pixel entity ID related to this manipulated data in stage 1.

In stage 2, the stage parser 82 fetches the pixel entity ID in theentity descriptor table 78 so that the pixel interpolation parameters incache memory 88 are communicated to the thread controller 56 innumerical pipe for a Z-interpolation operation. The resultingmanipulated data is returned to cache memory 88 and the stage parser 82queues the pixel entity ID in entity descriptor table 78. However, as analternative embodiment, stage 2 may be skipped if fixed function unit 21is utilized for Z-interpolation, as a nonlimiting example. In thisnonlimiting example, pixel packer 49 may thereafter receive datadirectly from the Z-interpolation unit (not shown).

Continuing this nonlimiting example, the pixel entity ID may becommunicated by the data transport system to receive pixel XYZ andmasked data, as directed by the stage parser and the data managementmove machine. At this time, the thread controller 56 may be engaged inexecuting other threads.

In stage 4 (FIG. 9), the stage parser 82 may acquire the pixel entity IDsuch that a texture interpolation operation is performed on the data incache memory 88, which may comprise repack interpolation parameters ofX, Y, Z and mask data information. As a result of this operation, stage4 may be concluded with pixel packet data stored in cache memory 88.Texture address data may be received by the data transport system 13upon forwarding processed information to other execution blocks forprocessing in stage 5. Depending upon the number of textures and thecomplexity of the pixel shader, stages 4, 5, and 6 may be replicated inarbitrary sequence. Nevertheless, as shown in stage 6, the pixel packetdata in cache member 88 may be manipulated in a texture filtering and/orcolor interpolation in pixel shader operations, in similar fashion asdescribed above. In the last stage, as shown in FIG. 9, stage parser 82directs the pixel entity ID to the data management move machine 52 suchthat the final pixel data is forwarded from the execution block forfurther processing and/or display.

As described above, the global spreader 12 may allocate a vertex,triangle, and/or pixel entity to one or more execution blocks forprocessing. While the description above depicts that the global spreader12 may allocate a vertex, triangle, or pixel packet to one or moreexecution blocks, at least one alternative embodiment provides that theglobal spreader 12 may make such allocations according to apredetermined priority preference.

FIG. 10 is a diagram 101 of a nonlimiting example flowchart depictingallocation of a triangle entity between the global spreader 12 and anexecution block of FIG. 1. In FIG. 10, a draw command may be received atstep 104 in the global spreader 12, which causes the global spreader 12to check the triangle input packet. If the triangle input packetcontains indices, step 106 may be executed in global spreader 12 suchthat the vertex table 43 is accessed in regard to the triangle packetreceived.

If the global spreader 12 determines that the vertices related to thetriangle packet are located in one execution block, the global spreader12 may create a local reference 108; however, if the global spreader 12determines that the vertices related to the triangle packet are locatedin multiple execution blocks, the global spreader 12 may create a globalreference 109 so that the processing of data on the multiple executionblocks can be orchestrated in parallel.

Global spreader 12 proceeds thereafter from step 108 or 109, dependingupon whether the vertices are located in one or a plurality of executionblocks to step 115, which operates to define a minimal amount ofresources for execution of the triangle packet. Data, in addition to theindices from step 104, may also be considered at step 115 so that anappropriate amount of resources may be allocated for the trianglepacket. Also, data related to the logical frame structure for executionof the triangle packet may also be considered at step 115.

Upon identifying a minimal amount of resources for execution as shown instep 115, the global spreader 12 generates an entity allocation requestat step 118. This entity allocation request includes an amount of datato be copied as produced by step 115, as well as a memory footprint alsofrom step 115. The entity allocation request step 115 may also receive adefined list of candidate execution blocks for receiving the entityallocation request, as well as a priority index for the entity type tobe executed.

As shown in step 120, the global spreader 12 checks the status of afirst execution block candidate, which may be according to the definedexecution block candidate list from step 111 and/or the priority relatedto the entity type to be executed. If the first execution blockcandidate has an available resource match for the allocated entity, theglobal spreader 12 sends an entity allocation request to the firstexecution block, as shown in step 126, and thereafter waits for receiptfrom the execution block upon completion. After the entity is allocated,global spreader 12 reverts back to step 104 to receive an additionalnext triangle drawing command.

However, if the first execution block candidate is not an availableresource match for the entity allocated in step 118, the global spreader12 resorts to a second execution block candidate, as shown in step 122.If this second execution block candidate is an available resource match,step 126 is executed, as described above. However, if the secondexecution block candidate is not a match, the global spreader 12 revertsto the third execution block candidate, as shown in step 124. Dependingupon whether this block is a match, the global spreader 12 may resort toone or more additional execution block candidates until a proper matchcandidate is found for allocating the entity to be processed.

This process described in FIG. 10 may not only occur for trianglepackets, but may also occur for vertex and pixel packets as well, as oneof ordinary skill in the art would know. However, in each instance, theglobal spreader 12 selects a candidate execution block as similarlydescribed above.

The foregoing description has been presented for purposes ofillustration and description. It is not intended to be exhaustive or tolimit the disclosure to the precise forms disclosed. Obviousmodifications or variations are possible in light of the aboveteachings. The embodiments discussed, however, were chosen, anddescribed to illustrate the principles disclosed herein and thepractical application to thereby enable one of ordinary skill in the artto utilize the disclosure in various embodiments and with variousmodifications as are suited to the particular use contemplated. All suchmodifications and variation are within the scope of the disclosure asdetermined by the appended claims when interpreted in accordance withthe breadth to which they are fairly and legally entitled.

1. A dynamically scheduled parallel graphics processor, comprising: aspreader configured to create graphic objects to be processed and toassign and distribute the created graphic objects for processing; aplurality of execution blocks coupled to the spreader and configured toreceive an assignment for processing a graphics object from the spreaderand to push the entity through one or more stages of processing, whereineach execution block schedules processing of the assigned graphicsobject, makes information about an assigned data object available to oneor more other execution blocks, and executes one or more instructionoperations on the assigned object; one or more fixed function unitscoupled to the spreader and the plurality of execution blocks andconfigured to execute one or more predetermined operations on a graphicobject; and an input/output unit coupled to the spreader, the one ormore fixed function units, and the plurality of execution blocksconfigured to provide access to memory external to the dynamicscheduling unit.
 2. The processor of claim 1, wherein the one or morefixed function units perform rasterization, texturing, or outputting ofpixel processing parts.
 3. The processor of claim 1, wherein thespreader allocates vertex graphic object entities associated with atriangle graphics object entity to an execution block also assigned toprocess the triangle graphics object entity.
 4. The processor of claim1, further comprising: logic in the spreader configured to maintain andupdate at each clock cycle for each execution block the amount ofavailable resources, the entities being processed, physical buffer datafor each entity, and available cache memory.
 5. The processor of claim1, further comprising: logic in the spreader configured to prioritizeeach execution block of the plurality of execution blocks for beingassigned a particular graphics object.
 6. The processor of claim 1,further comprising: logic executable by the spreader configured toestablish and maintain data layout preferences for triangle graphicobjects in association with corresponding vertices and pixels.
 7. Theprocessor of claim 1, wherein each of the plurality of execution blockscomprises: a stage parser containing pointers configured to point to anobject to be moved or processed; a controller configured to manageexecution of floating point and integer instructions; a descriptor tableconfigured to provide a registry of graphic objects being processed bythe execution block; and a data move machine configured to load and movegraphic objects in the execution block and further configured tocommunicate with the spreader and other execution blocks.
 8. Theprocessor of claim 7, further comprising: a rename logic tableconfigured to provide flexible address mapping of physical buffers in acache memory.
 9. The processor of claim 7, wherein the descriptor tablecontains information about data relation, allocation, readiness, andcurrent stage in association with the processing of a graphics object.10. The processor of claim 7, wherein the pointers contained in thestage parser table point to the graphics object to be processed on eachstage of a logical graphics pipeline.
 11. The processor of claim 10,wherein a process associated with a stage includes a numerical processinvolving a execution of floating point and integer instructions. 12.The processor of claim 10, wherein a process associated with a stageincludes a moving a graphics object data within the execution block, toanother execution block, or to the fixed function unit.
 13. Theprocessor of claim 7, wherein the descriptor table is a contentaddressable memory.
 14. The processor of claim 1, further comprising:logic in the spreader configured to maintain a primitive tablecontaining primitive ID information when a triangle entity is allocated.15. The processor of claim 14, wherein the primitive table has aprimitive ID field and an execution block field corresponding to aparticular execution block where a triangle entity is allocated.
 16. Amethod for dynamically scheduling the processing of graphics data in alogical graphics pipeline, comprising the steps of: creating an entityassociated with a packet of graphics data; selecting an execution blockbased on predetermined resource requirements and allocation information;assigning the entity to a selected execution block; allocating theentity in the selected execution block communicating graphics datarelated to the entity to the selected execution block; and pushing theentity through a plurality of processing stages.
 17. The method of claim16, wherein two or more execution blocks may be selected to performinstructions on graphics data related to the entity in parallel.
 18. Themethod of claim 16, further comprising the step of: indexing thegraphics data in a index buffer.
 19. The method of claim 16, furthercomprising the step of: registering the assigned entity in a table ofentities, wherein the registered entity is renamed each instance when anassignment is made to the table of entities.
 20. The method-of claim 19,wherein data associated with the renamed registered entity is used forsubsequent data reads for the entity in the table of entities.
 21. Themethod of claim 19, further comprising the steps of: pointing to anentity in the table of entities to be processed by the execution blockon a next stage of processing; processing the pointed entity accordingto one or more floating point or integer instructions if the entity isdesignated for numerical processing; and communicating the pointedentity by a data move unit to a predetermined logical location.
 22. Themethod of claim 21, wherein the pointed entity is communicated to afixed function unit for a predetermined graphics processing operation.23. The method of claim 16, wherein the graphics data associated withthe entity is processed according to one or more floating point andinteger instructions.
 24. The method of claim 16, further comprising thestep of: communicating the processed graphics data related to the entitydirectly to one or more additional execution blocks if the processedgraphics data is related to an entity assigned to the one or moreadditional execution blocks.